Data storage device calibrating fly height actuator based on read mode touchdown resistance of touchdown sensor

• US 9,001,453 B1
• Filed: 07/18/2014
• Issued: 04/07/2015
• Est. Priority Date: 07/18/2014
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Knigge, Bernhard E., Xu, Jian, Eaton, Robert E., Ye, Zhen
• Primary Examiner(s): Wong, K.
• Application Number:
  US14/335,724
• Time in Patent Office: 263 Days
• Field of Search: None
• US Class Current: 360/75
• CPC Class Codes: G11B 5/607 using thermal means
• CPC Class Codes: G11B 5/6076 Detecting head-disk contact

Abstract

A data storage device is disclosed comprising a disk, a head comprising a touchdown sensor, and a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting. The data storage device is configured into a read mode, and while in the read mode, the FHA setting is adjusted until the head contacts the disk and a touchdown read mode resistance of the touchdown sensor is measured. The data storage device is configured into a write mode and the FHA setting is adjusted so the head is not contacting the disk. While in the write mode, a non-touchdown write mode resistance of the touchdown sensor is measured, and a write touchdown FHA setting that will cause the head to contact the disk while in the write mode is estimated based on the touchdown read mode resistance and the non-touchdown write mode resistance.

Claims

1. A data storage device comprising:

a disk;

a head comprising a touchdown sensor;

a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting; and

control circuitry configured to;

configure the data storage device into a read mode;

while in the read mode, adjust the FHA setting until the head contacts the disk and measure a touchdown read mode resistance of the touchdown sensor;

configure the data storage device into a write mode and adjust the FHA setting so the head is not contacting the disk;

while in the write mode, measure a non-touchdown write mode resistance of the touchdown sensor; and

estimate a write touchdown FHA setting that will cause the head to contact the disk while in the write mode based on the touchdown read mode resistance and the non-touchdown write mode resistance.

2. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

while in the write mode, adjust the FHA setting and measure a non-touchdown write mode resistance of the touchdown sensor until the non-touchdown write mode resistance nears the touchdown read mode resistance; and

estimate the write touchdown FHA setting by extrapolating the non-touchdown write mode resistances toward the touchdown read mode resistance.

3. The data storage device as recited in claim 1, wherein the control circuitry is further configured to estimate the write touchdown FHA setting based on a delta from a read touchdown FHA setting that causes the head to contact the disk while in the read mode, wherein the delta is based on the touchdown read mode resistance and the non-touchdown write mode resistance.

4. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

while in the read mode, measure a non-touchdown read mode resistance of the touchdown sensor for a plurality of the FHA settings; and

estimate the write touchdown FHA setting based on the plurality of non-touchdown read mode resistances of the touchdown sensor.

5. The data storage device as recited in claim 4, wherein the control circuitry is further configured to:

first linear fit the plurality of non-touchdown read mode resistances and generate a delta representing a difference between the read mode FHA setting that causes the head to contact the disk and a FHA setting corresponding to a first intercept of the first linear fit with the touchdown read mode resistance of the touchdown sensor;

while in the write mode, adjust the FHA setting and measure a non-touchdown write mode resistance of the touchdown sensor for a plurality of the FHA settings;

second linear fit the plurality of non-touchdown write mode resistances of the touchdown sensor; and

estimate the write touchdown FHA setting based on the delta and a second intercept of the second linear fit with the touchdown read mode resistance of the touchdown sensor.

6. The data storage device as recited in claim 4, wherein the control circuitry is further configured to:

while in the write mode, adjust the FHA setting and measure a non-touchdown write mode resistance of the touchdown sensor for a plurality of the FHA settings; and

estimate the write touchdown FHA setting based on the plurality of non-touchdown read mode resistances of the touchdown sensor and the plurality of non-touchdown write mode resistances of the touchdown sensor.

7. The data storage device as recited in claim 6, wherein the control circuitry is further configured to:

measure a FHA setting delta between the plurality of non-touchdown read mode resistances of the touchdown sensor and the plurality of non-touchdown write mode resistances of the touchdown sensor; and

estimate the write touchdown FHA setting based on the FHA setting delta.

8. The data storage device as recited in claim 6, wherein the control circuitry is further configured to estimate the write touchdown FHA setting by subtracting the FHA setting delta from the read mode FHA setting that causes the head to contact the disk.

9. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

while in the read mode, measure at least one non-touchdown read mode resistance of the touchdown sensor;

measure an FHA delta setting between the non-touchdown read mode resistance of the touchdown sensor and the non-touchdown write mode resistance of the touchdown sensor; and

estimate the write touchdown FHA setting based on the FHA setting delta.

10. The data storage device as recited in claim 9, wherein the control circuitry is further configured to estimate the write touchdown FHA setting by subtracting the FHA setting delta from the read mode FHA setting that causes the head to contact the disk.

11. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

while in the write mode, measure at least one touchdown write mode resistance of the touchdown sensor;

measure a slope of a line passing through the touchdown write mode resistance and the touchdown read mode resistance; and

estimate the write touchdown FHA setting based on the slope of the line.

12. A method of operating a data storage device, the method comprising:

configuring the data storage device into a read mode;

while in the read mode, adjusting a fly height actuator (FHA) setting until a head contacts a disk and measuring a touchdown read mode resistance of a touchdown sensor;

configuring the data storage device into a write mode and adjust the FHA setting so the head is not contacting the disk;

while in the write mode, measuring a non-touchdown write mode resistance of the touchdown sensor; and

estimating a write touchdown FHA setting that will cause the head to contact the disk while in the write mode based on the touchdown read mode resistance and the non-touchdown write mode resistance.

13. The method as recited in claim 12, further comprising:

while in the write mode, adjusting the FHA setting and measuring a non-touchdown write mode resistance of the touchdown sensor until the non-touchdown write mode resistance nears the touchdown read mode resistance; and

estimating the write touchdown FHA setting by extrapolating the non-touchdown write mode resistances toward the touchdown read mode resistance.

14. The method as recited in claim 12, further comprising estimating the write touchdown FHA setting based on a delta from a read touchdown FHA setting that causes the head to contact the disk while in the read mode, wherein the delta is based on the touchdown read mode resistance and the non-touchdown write mode resistance.

15. The method as recited in claim 12, further comprising:

while in the read mode, measuring a non-touchdown read mode resistance of the touchdown sensor for a plurality of the FHA settings; and

estimating the write touchdown FHA setting based on the plurality of non-touchdown read mode resistances of the touchdown sensor.

16. The method as recited in claim 15, further comprising:

first linear fitting the plurality of non-touchdown read mode resistances and generating a delta representing a difference between the read mode FHA setting that causes the head to contact the disk and a FHA setting corresponding to a first intercept of the first linear fitting with the touchdown read mode resistance of the touchdown sensor;

while in the write mode, adjusting the FHA setting and measuring a non-touchdown write mode resistance of the touchdown sensor for a plurality of the FHA settings;

second linear fitting the plurality of non-touchdown write mode resistances of the touchdown sensor; and

estimating the write touchdown FHA setting based on the delta and a second intercept of the second linear fitting with the touchdown read mode resistance of the touchdown sensor.

17. The method as recited in claim 15, further comprising:

while in the write mode, adjusting the FHA setting and measuring a non-touchdown write mode resistance of the touchdown sensor for a plurality of the FHA settings; and

estimating the write touchdown FHA setting based on the plurality of non-touchdown read mode resistances of the touchdown sensor and the plurality of non-touchdown write mode resistances of the touchdown sensor.

18. The method as recited in claim 17, further comprising:

measuring an FHA setting delta between the plurality of non-touchdown read mode resistances of the touchdown sensor and the plurality of non-touchdown write mode resistances of the touchdown sensor; and

estimating the write touchdown FHA setting based on the FHA setting delta.

19. The method as recited in claim 17, further comprising estimating the write touchdown FHA setting by subtracting the FHA setting delta from the read mode FHA setting that causes the head to contact the disk.

20. The method as recited in claim 12, further comprising:

while in the read mode, measuring at least one non-touchdown read mode resistance of the touchdown sensor;

measuring an FHA delta setting between the non-touchdown read mode resistance of the touchdown sensor and the non-touchdown write mode resistance of the touchdown sensor; and

estimating the write touchdown FHA setting based on the FHA setting delta.

21. The method as recited in claim 20, further comprising estimating the write touchdown FHA setting by subtracting the FHA setting delta from the read mode FHA setting that causes the head to contact the disk.

22. The method as recited in claim 12, further comprising:

while in the write mode, measuring at least one touchdown write mode resistance of the touchdown sensor;

measuring a slope of a line passing through the touchdown write mode resistance and the touchdown read mode resistance; and

estimating the write touchdown FHA setting based on the slope of the line.